A simple method to develop 'watch lists' for invasive species

A simple method to develop 'watch lists' for invasive speciesKatelyn Faulkner1,2,3, Mark Robertson2,3, Mathieu Rouget2,4 and John Wilson1,21Invasive Species Programme, South African National Biodiversity Institute, Private Bag X7, Claremont, 7735.2Centre of Excellence for Invasion Biology, Private Bag X1, University of Stellenbosch, Matieland 76023Zoology and Entomology Department, University of Pretoria, Hatfield, 00284School of Agricultural, Earth and Environmental Sciences, University of KwaZulu Natal, Pietermaritzburg, 3209

Preventing the introduction of high-risk species is often the most logistically and economically efficient form of invasive species management. However, such preventative management strategies must focus on species with a high invasive potential, without unduly restricting personal freedom or commercial activities. To achieve this, methodologies for the prediction of invasive species have been developed around the world, including the development of ‘watch lists’ of species whose introduction should be prevented. However, the development of such watch lists are not always transparent or scientifically defensible. Using South Africa as a case study, we developed a rapid, easily repeatable invasive species risk assessment method. Three basic criteria: a history of invasion, climate match and propagule pressure were used to identify alien plants as either potential future invaders, non-invaders and those requiring further study. Additionally, the use of two climate match methods and three propagule pressure levels were assessed. The resultant models performed well (sensitivity ranged between 95 and 100%) and predicted that between 81 and 99% of alien plant species with a history of invasion elsewhere may have the potential to become invasive in South Africa. This is a promising technique that can be used in any region of the world for the rapid identification of potential threats.